Left wing protesters clashed with police in Berlin as a traditional May Day demonstration came to a halt far before reaching its intended end in the city center. Some demonstrators threw stones, bottles and firecrackers at the riot police, and officers responded with charges and batons. Arrests were made. The thousands strong demonstration had set off late on Tuesday afternoon from Berlin's neighborhood of Kreuzberg. Meanwhile in Hamburg, over one-thousand leftist activists gathered for the annual May Day protest march, local media reported. The demonstration - themed "No Alternative to Revolution" - saw protesters marching from St. Pauli to Ottensen. Right at the start, protesters threw fireworks at police officers, but the crowd remained mostly calm for the ensuing march. However, after a speech marking the end of the demonstration, violence erupted. Stones and bottles were thrown at the policemen escorting the march. Police responded employing pepper spray and arresting several protesters. Injuries were reported on both sides. Later on, riots broke out in Hamburg's Schanzenviertel neighborhood, a notorious site for May Day violence in past years.